Percutaneous transluminal coronary angioplasty (PTCA) is used to increase the lumen diameter of a coronary artery partially or totally obstructed by a build-up of cholesterol fats or atherosclerotic plaque. Typically a first guidewire of about 0.038 inches in diameter is steered through the vascular system near to the site of therapy. A guiding catheter, for example, can then be advanced over the first guidewire to a point just proximal of the stenosis. The guiding catheter typically terminates in a device outside of the patient that includes one or more ports for the introduction of other devices. One common device is typically referred to as a Y-connector.
After the guiding catheter is in position, the first guidewire is often removed. A balloon catheter on a smaller diameter second guidewire is then advanced within the guiding catheter to a point just proximal of the stenosis. The second guidewire is advanced into the stenosis, followed by the balloon on the distal end of the catheter. The balloon is inflated causing the site of the stenosis to widen.
Dilatation of the occlusion with a balloon can, however, form flaps, fissures and dissections which threaten reclosure of the dilated vessel or even perforations in the vessel wall. Implantation of a stent can provide support for such flaps and dissections and thereby prevent reclosure of the vessel or provide a patch repair for a perforated vessel wall until corrective surgery can be performed. Stents may measurably decrease the incidence of restenosis after angioplasty thereby reducing the likelihood that a secondary angioplasty procedure or a surgical bypass operation will be necessary.
A stent can be delivered as part of the dilatation procedure (with the stent mounted over the balloon). Alternatively, the stents can be delivered by yet another catheter inserted through the guiding catheter after the balloon catheter has been removed. This stent delivery catheter is typically inserted over the second guidewire used to guide the balloon into the stenotic region through the guiding catheter.
Among the problems facing those attempting to advance stent delivery catheters is the need to maintain the proper axial positions of the second guidewire relative to the stenotic region and also advance the stent delivery catheter over the second guidewire. In many cases, two people may be required to introduce the stent delivery catheter into the guiding catheter over the second guidewire, as well as advance the stent delivery catheter over the second guidewire to position the stent in the stenotic region for deployment.
Another problem associated with some introducers is that they are mounted on the stent delivery catheters by the user which typically requires the stent to be inserted through at least a portion of the introducer. That action may damage the stent or dislodge it from its proper mounting location on the stent delivery catheter.